Considerable attention has been focused in recent years on intravenous and intraarterial delivery of fluids to patients. Precision control over the rate at which such parenteral delivery occurs is of critical importance, inasmuch as improper administration of fluids can retard the recovery of patients or, in extreme situations, lead to further injury or even death. Early parenteral delivery systems relied on gravity flow to transfer fluid from a fluid container or reservoir to the patient. Attempts to accurately regulate gravity flow, however, proved difficult because the pressure forcing the fluid between the reservoir and the patient decreased as the fluid level within the reservoir dropped during the delivery operation. Thus, delivery rates in gravity-flow systems tended to vary in an unacceptable manner.
More recent parenteral delivery systems have employed pump motors in an effort to increase fluid delivery rate accuracy. Often, the pump motors comprise stepping motors which drive plunger or piston-like fluid pumps in response to suitable stepping motor control procedures. These procedures are highly compatible with the precision control requirements of parenteral administration because they provide the necessary degree of accuracy and are capable of implementation through reliable and efficient microprocessor programming techniques. U.S. Pat. No. 4,037,598 issued to Georgi on Jul. 26, 1977; U.S. Pat. No. 3,994,294 issued to Knute on Nov. 30, 1976; U.S. Pat. No. 3,985,133 issued to Jenkins et al on Oct. 12, 1976 and U.S. Pat. No. 3,736,930 issued to Georgi on Jun. 5, 1973 all disclose intravenous delivery systems wherein stepping motors are utilized in conjunction with camming mechanisms and pumping structures to achieve accurate delivery rate control. In spite of the advantages offered by prior art systems, however, certain improvements in the fluid delivery characteristics of existing delivery systems can be made. For example, none of the stepping motor control procedures associated with the stepping motors of the aforementioned patents compensate for non-linearities introduced into the fluid delivery rate as a result of interaction between the camming mechanisms, the stepping motors, and the pumping structures. Nor are efforts made to minimize the pulsatile discontinuities in fluid flow brought about by the interruption of fluid delivery during those portions of each pumping cycle devoted to refilling the pumping structures. Consequently, the prior art fails to provide a parenteral administration system capable of pumping precise amounts of fluid at linear rates in essentailly continuous fashion.